#include <stdio.h>
    #define MAXWORD 20
    #define LETTER 'a'
    #define DIGIT '0'
    #define NKEYS (sizeof keytab / sizeof(keytab[0]))
        /*whole bytes bytes in element*/
   main() /*count C keywords*/
{
int n, t;
int getword(char*, int);
char word[MAXWORD];
while ((t=getword(word, MAXWORD)) != EOF)
if (t== LETTER)
if ((n = binary(word, keytab, NKEYS)) >= 0)
keytab[n].keycount++;
for (n = 0; n < NKEYS; n++)
if (keytab[n].keycount > 0)
printf("%4d %s\n",
keytab[n].keycount, keytab[n].keyword);
}

binary(word, tab, n)/* find word in tab[0]...tab[n-1] */
char *word;
struct key tab[0];
int n;
{
int low, high, mid, cond;

low = 0;
high = n - 1;
while (low <= high) {
mid = (low+high) / 2;
if ((cond = strcmp(word, tab[mid].keyword)) < 0)
high = mid - 1;
else if (cond > 0)
low = mid + 1;
else
return (mid);
}
return (-1);
}
   
    struct key
    {
    char *keyword;
    int keycount;
    }
    keytab[]={
    "break", 0,
    "case",0,
    "char", 0,
    "const", 0,
    "continue", 0,
    "default", 0,
    /*...*/
    "unsigned", 0,
    "while", 0
    };
    
    
    getword(w, lim) /* get next word from input */
    char *w;
    int lim;
    {
    int c, t;
    
    if (type(c = *w++ = getch()) != LETTER)
    {
    *w = '\0';
    return(c);
    }
    while (-- lim > 0)
    {
    t = type (c = *w++ = getch());
    if (t != LETTER && t != DIGIT)
    {
    ungetch(c);
    break;
    }
    }
    *(w-1) = '\0';
    return(LETTER);
    }
    type(c) /* return type of ASCII character */
    int c;
    {
    if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z')
    return(LETTER);
    else if (c >= '0' && c <= '9')
    return(DIGIT);
    else
    return(c);
    }